Her family has a joke shared between them about her having a boyfriend. Meaning they find it completely impossible for her to get one and find it hilarious at the idea of her having one. That's how I read it.

My family would always put me down by belittling me and laughing at my love life.
I honestly thought this was how all families behaved towards each other until I met my husband to be.. His family actually help build me up. Years and years later they still try to put me down, that's just their way, but the thing is; I no longer believe their shitty comments!

"Ha-ha she has a boyfriend"
"Ha-ha I know right?" Your family is full of incredibly sad people if your relationship status is fuel for a "funny" ongoing joke. That would get old after the first time it was mentioned if someone in my family tried that shit about another person I loved.
Like... How could you possibly keep that joke going for a long time? FYL OP for unimaginative and mean-spirited, boring family.

lol "she" doesn't care what someone chooses to waste their time looking at. Boobs are everywhere, 98% of the adult female population has them. I really don't care about someone being able to see the top of my chest, it's just another body part.
Boobs or no boobs, this picture makes me laugh, so it's my default.